One of my favorite stores is Plato's Closet, a thrift shop chain that offers gently used name-brand apparel at deep discounts. On a recent visit I bought a pair of Diesel jeans for $25, and a pair of Lucky Brand jeans for $20. I used to shop there by myself, but suddenly, many of my friends are eager to join me. Seems their parents, shell-shocked by their brokerage statements, have tightened…